Examples of the types of systems in the railroad industry to which the invention may be applied include air drying systems or air brake control systems such as those produced and sold by the Westinghouse Air Brake Company (WABCO).
Representative of the type of environment to which the invention may be applied is the twin tower air drying system disclosed in U.S. Pat. No. 5,715,621. This twin tower air drying system is capable of providing a continuous stream of cleaned and dried compressed air to any of the various types of air brake control systems manufactured by WABCO. As shown in FIG. 3 of that patent, the twin tower system features two air drying assemblies (each containing a desiccant cartridge), two inlet check valves, two outlet check valves, two purge check valves and a control mechanism that coordinates operation of the check valves according to a preset operating cycle.
Whether used in air drying systems, brake control systems or other types of pneumatic apparatus, check and poppet type valve devices of varying design are used to establish, cutoff, or otherwise manipulate the flow of air in the systems in which they are employed. As shown in FIG. 1, one type of prior art check valve device is comprised of a valve element 1, a valve spring 2 and a valve seat 3, all of which accommodated within a chamber 4 defined in the housing of the valve device. The housing of the valve device also typically defines an inlet channel and an outlet channel by which the valve device pneumatically connects to or within the pneumatic system with which it is used. The valve chamber 4 is composed of one or more contiguous bores drilled into or otherwise formed in the valve housing. It is through this valve chamber 4 that the inlet and outlet channels interconnect.
Referring still to the basic features of the check type valve device of FIG. 1, the valve seat 3 features a surface 30 within which is defined an opening from which one of the channels emerges. The surface 30 of valve seat 3 may take, in part, the form of a raised seat ring 31. Typically made of rubber or other known elastomeric compound, the valve element 1 takes the form of a disk-shaped body whose width depends on the particular type of valve device at issue. Molded into the valve element is a metal (e.g., brass) insert 40 to endow the otherwise soft disk 1 with high degree of stiffness and strength. Projecting from the periphery of the elastomeric disk 1 is thus a plurality of metal prongs 5 so as to give the valve element 1 a fluted periphery, as best shown in FIG. 1A. The prongs thus aid the flow of air through the valve device. By these prongs, the valve element 1 is also guided in its movement within the main bore of the valve chamber 4. Formed at, or otherwise attached to, the seat facing side of the disk 1 is the valve head 10. The non-seat facing side of the disk typically takes the form of a short shaft or protuberance 11, as shown in FIG. 1. Typically held in compression between the non-seat facing side of the valve head 10 and a spring stop formed at one end of its bore in the valve housing, the spring 2 surrounds the protuberance 11. The spring 2 may also be held in compression between a snap ring secured to the cylindrical wall of its bore and the non-seat facing side of the valve head 10. The main bore of valve chamber 4 and the valve spring 2 together act as a guide to assure proper alignment of the valve head 10 with the valve seat 3. It is the valve spring 2 that provides the bias necessary to keep the valve head 10 in its normally closed position against the raised seat ring 31 of valve seat 3.
Shown in FIG. 2 is another type of prior art check valve device. This valve device is similar to that shown in FIG. 1 except for the structure of the valve element 1 and the valve seat 3. Specifically, the valve seat 3 features a flat rigid annular surface 32 rather than the raised ring seat 31 illustrated in FIG. 1. Correspondingly, the valve element 1 features a raised sealing ring 12 formed on the seat facing side of its valve head 10 rather than the flat sealing surface depicted in FIG. 1. Like the valve device shown in FIG. 1, the valve element 1 contains the metal insert 40. The valve element 1 is thus fluted in its periphery as it has the plurality of metal prongs 5 along its periphery, as shown in FIG. 2A. The main bore of chamber 4 and the valve spring 2 together act as a guide to assure proper alignment of the valve head 10 with the valve seat 3. The valve spring 2, of course, provides the bias necessary to keep the raised sealing ring 12 of valve head 10 in its normally closed position against the flat annular surface 32 of valve seat 3, as shown in FIG. 2.
Another type of prior art check valve device is illustrated in FIG. 3. This valve device features a valve element comprised of a circular elastomeric disk 50 and a molded plastic housing 60 in which the elastomeric disk 50 is housed. Akin to the metal insert 40 of the previously described valve devices, the plastic housing 60 provides stiffness to, strengthens and otherwise supports the soft elastomeric disk 50 so that it can resist deformation and otherwise withstand the stresses of the environment in which the valve element is used. Projecting from the periphery of the plastic housing 60 is a plurality of prongs 5. The prongs give the valve element a fluted periphery, as shown in FIG. 3A, and aid the flow of air through the valve device when the valve element, by the seat facing side of the elastomeric disk 50, is unseated from valve seat 3. It is also by these prongs that the valve element is guided in its movement within the main bore of valve chamber 4. Projecting from the surface 30 of valve seat 3 is a raised seat ring 31, as shown in FIG. 3. The valve spring 2 provides the bias necessary to keep the valve element in its normally closed position wherein the elastomeric disk 50 is sealingly positioned against the raised seat ring 31 of valve seat 3.
Referring now to the poppet type valve device shown in FIG. 4, this valve device features a valve element 1, a valve spring 2 and a valve seat 3 all within the chamber 4 defined in the housing of the valve device. The valve element 1 is comprised of a metal valve member 17 and an annular elastomeric seal 18. Projecting from the periphery of the metal valve member 17 is a plurality of prongs (not shown). As known to those skilled in the art of making valves, this gives the valve element a fluted periphery and aids in the flow of air through the valve device. The metal valve member 17 is typically made of brass, and defines an annular recess in its flat bottom surface 19. Molded into this annular recess is the annular elastomeric seal 18. The valve seat 3 features a raised seat ring 31. The valve spring 2 provides the bias necessary to keep the valve element 1 in its normally closed position wherein the annular elastomeric seal 18 is sealingly engaged against the raised seat ring 31 of valve seat 3. The poppet valve device further includes a piston actuated stem 70. One end of stem 70 is disposed in the lower channel with its head end opposite the center part of bottom surface 19 of metal valve member 17. An o-ring 71 is disposed in an annular recess defined in the cylindrical wall of stem 70. This o-ring prevents leakage of air from the valve device when the stem 70 is piston actuated further into the lower channel to unseat the valve element 1 from the raised seat ring 31 of valve seat 3.
Check and poppet type valve devices range from simple to complex in design. Quite often they must be manufactured to rather exacting dimensions so as to assure proper control and/or containment of air in systems that require relatively high operating pressure(s). Consequently, abutting valve surfaces must often be carefully machined so that the valve device when closed can provide an air tight seal between the corresponding surfaces of the valve element and the valve seat.
To resist deformation and otherwise withstand the stresses of the environment in which they are used, valve elements have traditionally been made so that they possess a high degree of stiffness and strength. Manufacturers such as WABCO, for example, have molded into their elastomeric valve elements 1, such as the ones shown in FIGS. 1 and 2, a brass insert 40 to endow the otherwise soft valve elements 1 with these characteristics. U.S. Pat. Nos. 5,213,749 and 5,303,937, assigned to WABCO and incorporated herein by reference, teach yet another type of prior art elastomeric valve element 41 into which a metal insert 61 has been molded.
There are several shortcomings inherent to check and poppet valve devices of the type that employ the soft valve elements 1 shown in FIGS. 1 and 2. The various prior art processes by which such stiffened valve elements are made are quite complex. During manufacturing, for example, the brass insert must be carefully loaded into, and positioned within, the mold so that the rubber or like compound can properly flow and form around the metal insert. Subsequent to the molding process, the flashing that is commonly produced during the molding operation must also be removed. These tasks add cost to both the manufacturing and quality control processes. Consequently, various alternatives to the use of brass inserts have been investigated, such as using a molded plastic housing 60 as a carrier for the type of sealing element 50 shown in FIG. 3. This type of housing provides the necessary rigidity and strength to the elastomeric sealing element. Unfortunately, the molded plastic housing option and various other alternatives, such as the one shown in FIG. 4, have also proven to be unduly complex and/or costly to implement.
The foregoing background information is provided to assist the reader to understand the invention described and claimed below. Accordingly, any terms used herein are not intended to be limited to any particular narrow interpretation unless specifically stated otherwise in this document.